1. Field of the Invention
The invention relates in general to a panel, and more particularly to a panel with a sealant blocker.
2. Description of the Related Art
Due to the high popularity of portable products, e.g., personal digital assistant (PDA) and cellularphone, the display technology develops rapidly. By employing a silicon plate, a glass plate, and liquid crystal molecules, a LCOS (liquid crystal on silicon) panel is more compact and has higher resolution than the traditional liquid crystal display (LCD), in which liquid crystal molecules are filled between two glass plates.
FIG. 1 is a cross section of a single pixel on a reflective-type LCOS. The LCOS has a lower plate 102 and an upper plate 101. The lower plate 102 includes a silicon substrate 103, and further includes a thin film transistor (TFT) 106, a capacitor 108, a pixel electrode 110, scan lines 107, data lines 111, and a reflective layer 112 on the silicon substrate 103, wherein the scan lines 107 are parallel to each other and so are the data lines 111. The upper plate 101 includes a glass substrate 120 and an opaque electrode 118, such as ITO electrode, on the glass substrate 120.
The upper plate 101 and the lower plate 102 are opposite to each other, and the gap between the two plates is filled with liquid crystal molecules. The liquid crystal molecules with spacers 132 constitutes a liquid crystal layer 114. A sealant 130 is next to the liquid crystal layer 114. The sealant 130 is used to connect the upper plate 101 and the lower plate 102, and the spacer 132 is used to support the spacing of the gap. The spacer 132 can be formed by direct spraying. To distinguish photo spacers from the other spacers, the photo spacers are labeled as 132(2), and the other spacers are labeled as 132(1).
The driving circuit of LCOS applies a voltage signal to the pixel electrode 110 to control the operations of each pixel by enabling scan lines 107 and data lines 111. The polarization of the light passing through the liquid crystal layer 114 is modulated by the alignment of the liquid crystal molecules in the liquid crystal layer 114, which varies with the voltage applied to the pixel electrode 110. After the incident ray (labeled as I in FIG. 1) passes through the liquid crystal layer 114, the reflected ray (labeled as O in FIG. 1) is produced by the reflective layer 112 and passes through a polarizing film (not shown in FIG. 1). The polarized reflected ray O has the brightness corresponding to the voltage applied to the pixel electrode 110.
Another method to form a uniform gap, which is more commonly used now a days, is to apply a long-shaped photo spacer in the spacing between the pixels. Referring to FIG. 2, it shows a cross-sectional view of LCOS with long-shaped photo spacer 205 before the upper plate 201 and the lower plate 202 are compressed. The manufacturing of the upper plate 201 and the lower plate 202 are completed respectively. The lower plate 202 has the long-shaped photo spacers 205, extending upwardly and including an optical fiber therein. Then, a sealant 203 is also formed on the periphery of the lower plate 202. The upper plate 201 and the lower plate 202 are aligned to each other and are compressed towards each other. After the compressing of the upper plate 201 and the lower plate 202, the width of the gap can be sustained to be uniform by the long-shaped photo spacer 205.
Referring to FIG. 3, it shows a LCOS with the liquid crystal molecules filled in cell room 304 of each pixel. The cell room 304 is the spacing separated by the long-shaped photo spacer 305. After the compressing, liquid crystal molecules are injected into the cell rooms 304 and the manufacturing of the LCOS is completed.
However, the sealant utilized in FIG. 2 and FIG. 3 will contaminate the liquid crystal molecules in the peripheral cell room 304(1), which is disposed on the edge of the lower plate 302. And the polluted and un-polluted liquid crystal molecules will have different alignments, although the voltage signals applied to the pixel electrodes are the same. Therefore, the display quality on the panel edge is not consistent with the other area of the panel.
Furthermore, a hot pressing process is needed to cure the sealant to seal the upper plate and the lower plate tightly. The high temperature of the hot pressing process on the devices of the upper plate and the lower plate, and shortens the panel lifetime.
Moreover, the structure of the LCOS is easily destroyed by the hot pressing process due to the different coefficient of expansion for the sealant, upper plate, and lower plate. So that the residual stress will decrease the yield of the LCOS.
Also, a UV gel, which is a substitute of the sealant 303, is cured by irradiating UV light and does not have the disadvantages caused by the hot pressing process. However, the liquid crystal molecules are polluted more seriously by the UV gel than by the sealant, which limits the using of the UV gel in the traditional method.